Kitchen window exploded... can you tell us why?

We're renting a house. The window in the kitchen is about 20 years old. Its seal has been broken since we moved in (fogging, etc.), if that matters at all.

We're in Minnesota, so it is fairly cold. It was about 30 degrees today when the window broke. We keep our house at about 68.

Today, I burned a batch of cookies. A tragedy in itself, but it got worse. My husband opened the window (casement style crank) about 2 inches, to air out the kitchen from the burned smell. It was left this way for maybe 3-5 minutes. Then he turned the crank to close it. We heard a gunshot-like popping sound and the window shattered from the center of the window outward, just like that!

This is not the first window we've opened in the cold in our lives, but we've never, ever had this happen before! So, what on earth happened?

Here is my experience with what happened to you. On certain insulated glass packages, after the glass goes through the oven that seals the unit and it begins to cool, this happens. As the sealed unit cools, the glass units begin to hour glass - or bow toward each other. You may have noticed this affect on houses or other buildings in your area.
In your situation, you burnt cookies which probably heated up the room. When the window was opened the hour glassed units contracted, the two lites of glass contacted each other and shattered.
This also happens as windows are tested. The window/door is put under loads and sometimes the glass contacts each other and literally explodes.
Just speculation.

It's possible the inside pane of glass became very warm. When glass becomes warm, it expands. When the window was opened, it was exposed to a sudden blast of cold air and the glass contracted quickly causing it to shatter. I had something similar to this happpen a few years ago when we got a cold front moving thru and the cold air and rain hit a tempered glass table on my deck and caused it to suddenly shatter.

Either that or The Flying Cookie Monster was punishing you for the burnt cookies.

That's a good answer by "sky". We've seen glass break in the same respect on projects, while we are still constructing. Deep soffits will often shade a cold upper portion of window's glass. If the afternoon sun moves over the top of the house and exposes the lower portion of the western elevation's glass to an excessive amount of immediate heat, the glass will sometimes crack.

Does not sound like very well-tempered glass, nor a well made window unit. Imagine if your Pyrex measuring cups behaved like this.

They can make a tempered glass 2-pint measuring cup that safely goes from freezer to oven for $5, but not a much more expensive window unit that will handle the typical daily environment of cold and sun? Is it physics, or the corrupt doings of The Glazing Cartel? (I jest not about The Cartel; in specialized applications/locations (e.g. HVHZ), the # total of suppliers is often 1, or at most 2.)

We The Consumers are perhaps not getting our hard-earned $$ worth. Often a class-action suit by the Attorneys General of several states is just the ticket to get the QC dept. to tighten things up a bit. ;')

Sorry about your exploding window. Hope your landlord is not an *-hole about it.

One hears so many sad tales of the whiz-bang double-pane offerings. I always did fine, in PA and CO, w/ single pane windows, supplemented by storm windows... of course the rapid airing of the kitchen scenario becomes a tad more problematic... pros and cons, no simple answers.

The inside of the window was not hot at all. It was only 68 in the house, it wasn't sunny outside, there was no fire from the cookies, just a little smoke from the oven, etc. I would be amazed if a window can't handle a 38 degree temp difference. That's terrible! I really can't imagine it was a temperature shock, especially because it didn't happen until the window was closed.